Combustion cap floating collar using E-seal

ABSTRACT

An improved floating collar assembly for gas turbine combustion units consists of a sheet metal collar with a flat flange and an E seal that is pre-compressed within a block of epoxy. The collar fits over a corresponding fuel nozzle burner tube and is retained on a cap assembly by a flat plate. During assembly, the collar is loose so that it floats, which makes cap assembly easy. During operation, the epoxy used to pre-compress the E seal heats up and burns off, whereupon the E seal opens up and produces a seating load between the collar and plate that is high enough to keep the collar from rotating and thereby reduce collar wear.

The present invention relates to gas turbines, and, more particularly,to a combustion cap floating collar for gas turbine combustion units.

BACKGROUND OF THE INVENTION

A gas turbine combustion system typically consists of several combustionchambers and, inside each chamber, there are several fuel nozzleassemblies. Positioned over the fuel nozzles is a cap assembly equippedwith matching number of floating collars which are held insidecorresponding counter bores by a retaining plate. When installed, thesefloating collars fit over the outside surface of fuel nozzle burnertubes and function as air leak limiters. Most cap floating collarsexperience severe wearing during combustion operation and have to bereplaced, resulting in operating cost and reliability being significantissues. Analysis of the worn collars has shown that collar rotationduring the operation is the cause of the collars failure. As thefloating collars rotate, there is frictional wearing between the collarsand a backing plate.

BRIEF DESCRIPTION OF THE INVENTION

The present invention is an improved cap floating collar assembly forgas turbine combustion units that reduces floating collar wear, tothereby improve floating collar reliability. The floating collarassembly fits over a corresponding fuel nozzle burner tube and isretained by a flat plate in a counter-bore on the cap assembly. Thecollar assembly consists of two parts, i.e., a sheet metal collar with aflat flange and an E seal that is pre-compressed within a block ofepoxy. During assembly, the collar is loose so that it floats, whichmakes cap assembly easy. This feature is also a very importantrequirement for field service. When the gas turbine starts to run, theepoxy used to pre-compress the E seal heats up and burns off, whereuponthe E seal opens up and produces a seating load between the collar andplate that is high enough to keep the collar from spinning, to therebyreduce collar wear.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a cap assembly covering several fuel nozzleassemblies.

FIG. 2 is a top perspective view of the fuel nozzle assemblies shown inFIG. 1 without the cap covering them and being mounted on an end cover.

FIG. 3 is a bottom perspective view of the inside of the cap assemblyshowing several counter bores in which the fuel nozzle assemblies areinserted and corresponding floating collars that are held in the counterbores by retaining plates.

FIG. 4A is a simplified side elevational and partial cross-sectionalview of a fuel assembly.

FIG. 4B is a partial side elevational, cross-sectional view of a portionof the fuel assembly shown in FIG. 4A.

FIG. 5A is a side elevational, cross-sectional view of an E seal used aspart of the collar assembly of the present invention.

FIG. 5B is a top plan view of the E seal of FIG. 5A.

FIG. 6 is a partial side elevational, cross-sectional view of thefloating collar and E seal of the present invention mounted in a capassembly and engaging a fuel nozzle tube.

FIG. 7 is a schematic, bottom perspective view of the floating collar ofthe present invention engaging a fuel nozzle tube and being held insideof the cap assembly by a retaining plate.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a top plan view of a combustion cap assembly 10 for a gasturbine with five fuel nozzle assemblies 12 within five correspondingcounter bores 20 in cap assembly 10. Cap assembly 10 is mounted withincombustor 15.

FIG. 2 is a top perspective view of the five fuel nozzle assemblies 12from FIG. 1 shown being bolted to an end cover 17. Each of the fuelassemblies 12 includes a burner assembly 14 that is located within acorresponding fuel nozzle tube 16. Each fuel nozzle tube 16 includes ashoulder 18 corresponding to a change in the outside diameter of thefuel nozzle tube. As described in greater detail below, the shoulder 18of fuel nozzle tube 16 engages a floating collar 22 that is part of thefloating collar assembly of the present invention.

FIG. 3 is a bottom perspective view of the cap assembly 10 shown inFIG. 1. Cap assembly 10 includes the five counter bores 20 shown inFIG. 1. Within the counter bores 20 are five corresponding floatingcollars 22 that are held in place by four retaining plates 24 attachedto the bottom side of cap assembly 10. The manner in which the floatingcollars are held by plates 24 is described in greater detail below withrespect to FIG. 6.

FIG. 4A is a simplified and partial side cross-sectional view of a fuelburner assembly 12, the majority of the details of which are notrelevant to an explanation of the floating collar assembly of thepresent invention. FIG. 4A shows a fuel nozzle tube 16 and a fuel burner14 located within tube 16 in cross section and a floating collar 22,also in cross section, positioned over the exterior of fuel burner tube16.

FIG. 4B is an enlarged cross-sectional view of a portion of the fuelnozzle tube 16 and the floating collar 22 shown in FIG. 4A to bettershow the manner in which the floating collar engages the fuel burnertube 16 when it is position over the exterior of fuel burner tube 16. Ascan be seen in FIG. 4B, the fuel burner tube 16 includes a shoulder 18that constitutes a change in the outside diameter of fuel burner tube16. Floating collar 12 engages shoulder 18 of fuel burner tube 16 whencounter bore 20 in cap assembly 10 is positioned over tube 16 as capassembly is attached to a fuel burner assembly.

FIGS. 5A and 5B are a side, cross-sectional view and a top plan view,respectively, of a sealing spring 23 used to hold the floating collar 22in place during burner operation. As can be seen in FIG. 5A, preferably,sealing spring 23 has a shape, in cross-section, that is similar thecapital letter “E”, although it should be noted that sealing springswith other shapes could be used in the present invention. As can be seenin FIG. 5B, preferably, sealing spring 23 5 has a plan view shape thatis substantially circular so as to allow sealing spring 23 to also bepositioned over the exterior of fuel burner tube 16.

In its E shape preferred embodiment, sealing spring 23 has a centersection 28 shaped like a hairpin and two curved ends 26 that connect atone end to center section 28 to complete the cross-sectional “E” shapeof sealing spring 23. As can also be seen from FIG. 5A, the preferred“E” shape of sealing spring 23 results in a spring configuration thatcan be compressed to produce a force acting counter to the compressionof sealing spring 23. Here again, it should be noted that sealingsprings with other compressible shapes that produce a similarcounter-acting force could be used in the present invention.

FIG. 6 shows the cap floating collar design of the present inventionwhen it is initially installed in the cap assembly of a gas turbine. Asshown in FIG. 6, the cap assembly 10 includes a shoulder 32, which isengaged by a flat flange 30 of floating collar 22. Positioned over flatflange 30, between cap 10 and retaining plate 24, is sealing spring 23.As can be seen in FIG. 6, sealing spring 23 is initially encased in ablock of epoxy 34. As can also be seen from FIG. 6, the floating collar22 has a “curvy” shape to it, such that as it extends from flat flange30, it curves inwardly and outwardly towards and away from the side wallof fuel burner tube 16 so that a first curve 36 of collar 22 engagestube 16 at a first location and a second curve 38 of collar 22 engagestube 16 at tube shoulder 18.

FIG. 7 is a perspective, schematic view of the floating collar 22 of thepresent invention installed on the cap assembly 10 and surrounding afuel nozzle tube 16. Here again, it can be seen that the floating collar22 is held in place with respect to the cap assembly 10 by the retainingplate 24, such that when the fuel nozzle tubes 16 that are part of thefuel nozzle assembly 12 are inserted into the cap assembly 11, thefloating collar 12 engages the outside wall of the fuel nozzle tube 16.

During operation of the gas turbine, the epoxy block 34 initiallyencasing sealing spring 23 heats up and burns off, whereupon sealingspring 23 is able to open up and produce a seating load high enough tokeep the floating collar 22 from spinning around fuel nozzle tube 16during operation of the gas turbine. The load is exerted between the capassembly 10 at the shoulder 32 and the retaining plate 24 engaging thebottom side of sealing spring 23.

Thus, in the present invention, for a typical cap assembly there arefive floating collars 22 that are held inside of cap assembly 10 bycorresponding retaining plates 24. Once the cap assembly 10 is installedover the fuel nozzle assemblies 12, which include the fuel nozzles 14mounted on the end cover 17, the fuel nozzles 14 fit through the counterbores 20 in the cap assembly 10. Upon final assembly, the floatingcollars 22 rest or sit on an outside surface of the nozzle tubes 16, andultimately are held in place by the expansion of corresponding sealingspring 23 that produce the seating loads upon the heating up and burningoff of the epoxy blocks 34 that are used to initially compress sealingspring 23. Expansion of sealing springs 23 and the resulting seatingloads prevents the floating collars 22 from rotating during burneroperation. This, in turn, reduces the wear of the floating collars tothereby improve their reliability.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. At least one floating collar assembly for a cap of a combustion unitcontaining at least one fuel nozzle assembly corresponding to the atleast one floating collar assembly, each of the at least one fuel nozzleassemblies including a fuel nozzle burner tube, each of the at least onefloating collar assemblies comprising: a floating collar positionedaround a side wall of a corresponding fuel nozzle burner tube, thecollar including a flange for engaging the cap, the flange beingsubstantially parallel to the side wall of the burner tube when thefloating collar is positioned around the side wall, and a sealing springpositioned between the flange and a plate attached to the cap, the platebeing substantially parallel to the side wall of the burner tube whenthe cap and plate are positioned over the burner tube, the sealingspring producing a seating load between the collar flange and the plateto hold the flange against the cap and thereby prevent the floatingcollar from rotating during combustion unit operation.
 2. The floatingcollar assembly of claim 1, wherein the collar is substantially circularand positioned over an exterior of the fuel nozzle burner tube so as toengage a shoulder in the tube exterior when the cap is attached to thecombustion unit.
 3. The floating collar assembly of claim 2, wherein thesealing spring is substantially circular and extends around the exteriorof the fuel nozzle burner tube when the cap is attached to thecombustion unit.
 4. A floating collar assembly for a combustion unitcap, the floating collar assembly comprising: a collar including aflange for engaging the cap, and a sealing spring positioned between theflange and a plate attached to the cap, the sealing spring producing aseating load between the collar flange and the plate to hold the flangeagainst the cap and thereby prevent the collar from rotating duringcombustion unit operation, wherein the collar is substantially circularand positioned over an exterior of a fuel nozzle burner tube so as toengage a shoulder in the tube exterior when the cap is attached to thecombustion unit, and wherein the collar has a first curve that engagesthe tube exterior at a first location and a second curve that engagesthe tube exterior at the tube shoulder.
 5. The floating collar assemblyof claim 1, wherein, during assembly of the cap to the combustion unit,the collar is loose.
 6. The floating collar assembly of claim 5,wherein, during assembly of the cap to the combustion unit, the sealingspring is held in a compressed position by epoxy.
 7. The floating collarassembly of claim 6, wherein, during combustion unit operation, theepoxy heats up and burns off, whereupon the sealing spring isdecompressed and produces a seating load between the collar flange andplate so as to keep the collar from spinning during combustion unitoperation to thereby reduce collar wear.
 8. The floating collar assemblyof claim 1, wherein the sealing spring has a shape, in cross-section,that is similar the capital letter “E”.
 9. The floating collar assemblyof claim 8, wherein the sealing spring has a center section shaped likea hairpin and two curved ends that connect at one end to center sectionto complete the cross-sectional “E” shape of the sealing spring.
 10. Thefloating collar assembly of claim 1, wherein the cap includes ashoulder, which is engaged by the flange of the floating collar.
 11. Atleast one floating collar assembly for a cap of a combustion unitcontaining at least one fuel nozzle assembly corresponding to the atleast one floating collar assembly, each of the at least one fuel nozzleassemblies including a corresponding fuel nozzle burner tube, each ofthe at least one floating collar assemblies comprising: a substantiallycircular floating collar positioned around a side wall of acorresponding fuel nozzle burner tube, the collar including a flatflange for engaging the cap, the flange being substantially parallel tothe side wall of the burner tube when the floating collar is positionedaround the side wall, and a substantially circular, compressible sealingspring positioned between the flat flange and a flat plate attached to aback side of the cap, the plate being more perpendicular than parallelto the side wall of the burner tube when the cap and plate arepositioned over the burner tube, the sealing spring producing a seatingload between the collar flange and the flat plate to thereby hold theflange against the cap and prevent the floating collar from rotatingduring combustion unit operation.
 12. The floating collar assembly ofclaim 11, wherein the collar is positioned over an exterior of the fuelnozzle burner tube so as to engage a shoulder in the tube exterior andthe sealing spring extends around the exterior of the fuel nozzle burnertube when the cap is attached to the combustion unit.
 13. A floatingcollar assembly for a combustion unit cap, the floating collar assemblycomprising: a substantially circular collar including a flat flange forengaging the cap, and a substantially circular, compressible sealingspring positioned between the flat flange and a flat plate attached to aback side of the cap, the sealing spring producing a seating loadbetween the collar flange and the flat plate to thereby hold the flangeagainst the cap and prevent the collar from rotating during combustionunit operation, wherein the collar is positioned over an exterior of afuel nozzle burner tube so as to engage a shoulder in the tube exteriorand the sealing spring extends around the exterior of the fuel nozzleburner tube when the cap is attached to the combustion unit, and whereinthe collar has a curvy shape, such that as it extends from the flatflange, it curves towards and away from the exterior of the fuel nozzleburner tube, whereby a first curve of the collar engages the tubeexterior at a first location and a second curve of the collar engagesthe tube exterior at the tube shoulder.
 14. The floating collar assemblyof claim 11, wherein, during cap assembly, the collar is loose so thatit floats and the sealing spring is pre-compressed within a block ofepoxy.
 15. The floating collar assembly of claim 14, wherein the epoxyheats up and burns off during operation of the combustion unit,whereupon the sealing spring is decompressed and engages the flat flangeand flat plate to produce the seating load between the collar and platethat keeps the collar from spinning during combustion unit operation tothereby reduce collar wear.
 16. The floating collar assembly of claim11, wherein the sealing spring has a shape, in cross-section, that issimilar the capital letter “E”.
 17. The floating collar assembly ofclaim 16, wherein the sealing spring has a center section shaped like ahairpin and two curved ends that connect at one end to center section tocomplete the cross-sectional “E” shape of the sealing spring.
 18. Thefloating collar assembly of claim 1, wherein the cap includes ashoulder, which is engaged by the flat flange of the floating collar.19. A method of securing at least one floating collar within acombustion unit cap to keep the collar from spinning during combustionunit operation to thereby reduce collar wear, the combustion unitcontaining at least one fuel nozzle assembly corresponding to the atleast one floating collar, each of the at least one fuel nozzleassemblies including a corresponding fuel nozzle tube, the methodcomprising the steps of: providing a circular floating collar around anexterior side wall of a corresponding fuel nozzle burner tube, thecollar including a flat flange that is substantially parallel to theside wall of the burner tube when the collar is positioned around theside wall, positioning the collar adjacent to a circular a shoulderformed in the cap, positioning an “E” shaped sealing spring that ispre-compressed in epoxy adjacent to the collar's flat flange, attachinga plate to the cap so as to position the “E” shaped sealing springbetween the flat flange and the plate and thereby allow the collar tofloat between the plate and the shoulder formed in the cap, andattaching the cap to the combustion unit, whereby the collar ispositioned over the exterior side wall of the fuel nozzle burner tube soas to engage a shoulder in the tube exterior, the plate beingsubstantially parallel to the exterior side wall of the burner tube whenthe cap and plate are positioned over the combustion unit.
 20. Themethod of claim 19 further comprising the step of operating thecombustion unit so that the epoxy heats up and burns off, whereupon the“E” shaped sealing spring decompresses and engages the flange and plateto produce a seating load between the collar flange and plate that keepsthe collar from spinning during combustion unit operation to therebyreduce collar wear.